Radio-frequency coil and electrostatic shield



Sept. 29, 1942.

Pm/e ART R. LUDERITZ RADIO-FREQUENCY COIL AND ELEC TROSTATIC SHIELD Filed Oct. 18, 1940 79/0655 /4 75/5 RING REMAIN (0/1750 INVENTOR Nada [f ll'ide'liiz BY wm ATTO R N EY Patented Sept. 29, 1942 RADIO-FREQUENCY COIL AND ELECTRO- STATIC SHIELD Rudolf Liideritz, Berlin, Germany; vested in the Alien Property Custodian Application October 18, 1940,Serial No. 361,664

Germany June 8, 1939 3 Claims. (01. 25016) This invention relates to a method of producing radio-frequency coils and static shields which are particularly adapted to use in the shortwave band, while employing ceramic supporting materials.

It is known in the art to make radio frequency coils placed upon ceramic supports or forms in a manner such that a coat of metal is provided upon the ceramic material, say, by electro-plating, spraying, etc., whereupon the resulting metallic layer is subdivided to result in the turns of a coil by making spiral incisions or grooves therein. This method known in the earlier art involves the drawback that the metallic coat produced by plating or metallizing fails to stick with sufllcient tenacity upon the surface of the ceramic body so that the coat is liable to scale off in the subsequent milling work.

According to the invention to avoid the said drawback the metallization or metallic coat is provided upon a ceramic body or support which has previously been furnished with grooves and slots, there being employed subsequent grinding or abrasion of the portions of the metal-coated ceramic body as has remained between the grooves or slots. The form and position of the latter depends upon the shape of the conductor structure which is desired. For instance, if a coil is to be made, then the groove must be formed spirally, while for making an electrostatic shield preferably paralleled grooves are provided.

The basic idea of the invention shall now be explained more fully by reference to the appended drawing wherein Figs. 1 and 2 each show prior art constructions; Fig. 3a shows a longitudinal section along line aa of Fig. 31) looking in the direction of the arrows; Fig. 3b shows the exterior of a shield can constructed according to the invention; Fig. 3c shows a horizontal section through the can of Fig. 3b along line cc looking in the direction of the arrows, the sectioning of the can and the exterior slots, or grooves, being partially shown; and Fig. 4 shows a section along line 4-4 of Fig. 31) looking in the direction of the arrow. Fig. 1 is a longitudinal section taken through one end or side of a cylindrical coil. The ceramic body i has a circumferential spiral groove 2 of semi-circular cross-sectional shape. Between the various grooves is a narrow dam 3 of ceramic material. This coil support or body is thereupon provided with a metallic coat 4 by ways and means well known in the art. Because of the large curved surface which the grooves provide for the metallic coat firm adherence of the metallic coat is insured. By grinding away of portions of the metal coat down to the ceramic material the metallic surface, according to the width of the groove, is divided into a spiraled band or ribbon as indicated on the right-hand side in Fig. 1.

It will be understood that the grooves could also be of a different shape, say, as shown in Fig. 2 with a triangular cross-sectional form. This offers the practical advantage that the distance between the various turns can be regulated at will by regulating the depth of material removed by abrasion. The numerals in Fig. 2 signify the same elements as in Fig. 1.

Figs. 3a to 30 and Fig. 4 illustrate an electrostatic shield which ls made by the method of the invention. A ceramic body or can 5, for instance of cylindrical form, has semi-circular slots, or grooves, 6 provided on its exterior periphery extending in a direction parallel to the vertical axis. The grooves 6 are shown in crosssection in Fig. 4. As previously explained, the grooves 6 are completely coated with metal. The entire exterior vertical surface of shell 5 is so coated. The metal is ground away at the ridges so as to expose the ceramic material. In Fig. 4 the metal coat is designated as 6', while the numeral 5' designates the exposed ceramic material at the ridges between grooves 6. In order for the metal grooves to be electrically connected, the lower peripheral section 1 of the shell does not have the ridges ground down. It is to be clearly understood that numeral 1 denotes a comparatively narrow ring located completely around the ceramic body 5 adjacent flange 8 provided with the spaced apertures 9. The ridges between grooves 6 in this narrow ring! are permitted to remain coated with metal, as indicated by the legend in Fig. 3!).

I claim:

1. The steps in a method of making an electrostatic shield which comprise coating one of the surfaces of a tubular ceramic body, which surface is provided with a plurality of closely adjacent thin individual alternate grooves and ridges extending substantially parallel to each other and to the axis of the tubular body, with a thin layer of conducting material, and then removing said coating from all of the ridges separating said grooves excepting for a portion of each ridge which is included in a comparatively narrow ring located completely around saidbody and whose axis coincides with the axis of said body.

2. The steps in a method of constructing an electrostatic shield which comprise providing one of the suriaces of a tubular ceramic member with a plurality of alternate ridges and grooves extending substantially the full length of the tubular member and parallel to each other and 5 the axis of the tubular member, coating said surface with a'thin layer oi. conducting material and then removing said coating from each of the ridges excepting for a narrow portion of each ridge which is located adjacent one edge 16! of said tubular member.

3. The steps in a method of constructing an electrostatic shield which comprise providing the two opposite surfaces of a tubular ceramic said surfaces with a thin layer of conducting material and then removing said coating from each or said ridges excepting from a portion of each which is included in a strip which is completely around said tubular body.

RUDOLF LUDERITZ. 

